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561.
562.
Andrew J. G. Baxter Pamela Davis Roger J. Ponsford Robert Southgate 《Tetrahedron letters》1980,21(52):5071-5074
3-(2-Pyrimidinylthio-) substituted olivanic acid analogues, with and without a C-6 hydroxyethyl substituent, have been synthesised in high yield using an intramolecular Wittig reaction followed by deprotection to afford zwitterions with high antibacterial activity. 相似文献
563.
Lovely Begum Jane L. Humphreys Pamela R. Russi Roger C. Whitehead 《Tetrahedron letters》2004,45(33):6249-6253
Exploitation of the dual dehydrating and fluorodeoxygenating properties of the dialkylaminosulfurtrifluorides has allowed access to the C3-fluorinated analogues of (−)-shikimic acid. 相似文献
564.
Gilbert J. Matare Kevin M. Kane Pamela J. Shapiro Ashwani Vij 《Journal of chemical crystallography》1998,28(10):731-734
cis-[(1,2-diphenyl-1,2-dicyclopentadienyl)ethanediyl]bis(tetrahydrofuran)calcium is prepared by reductively coupling phenylfulvene with activated calcium to produce cis and trans isomers which can be separately crystallized. The cis isomer crystallizes in the monoclinic space group P21/c. The cell parameters are: a = 9.7006(1), b = 18.9839(1), c = 14.2018(2) Å, = 91.263(1)°, V = 2614.70(5) Å3, D
calc = 1.252 mg/m3, and Z = 4. Spectroscopic and crystallographic data for the cis-isomer are presented and discussed. 相似文献
565.
Schmidt-Rose T Pollet D Will K Bergemann J Wittern KP 《Journal of photochemistry and photobiology. B, Biology》1999,53(1-3):144-152
The heat-shock response is a cellular defence mechanism against environmental stresses that is evolutionarily conserved from bacteria to man. Numerous reports demonstrate the beneficial effects of heat-shock protein induction on cell survival under toxic or oxidative stress, e.g., in cardiac and cerebral ischemia or prior to organ transplantation. However, there is little data on the effects of heat treatment on damage caused by UV irradiation. Applying three independent techniques, we have tested the influence of thermal pretreatment of skin cells (1 h, 43 degrees C) on the initial extent of UV-B-induced DNA damage and its subsequent repair. For cultured human epidermal keratinocytes and dermal fibroblasts we can show reduced levels of nucleotide-excision-repair-associated DNA strand incision in the comet assay. Moreover, immunostaining and flow cytometric quantitation of thymidine dimers immediately and one day after irradiation, respectively, reveal that the initial DNA damage is not (keratinocytes) or only moderately (fibroblasts) lower in heat-shocked cells as compared to untreated controls. However, excision repair of dimers is significantly attenuated during the first 24 h in both cell types. Furthermore, using a modified host-cell reactivation assay, we are able to demonstrate that repair of UV-B-damaged plasmid DNA is lower if the transfected cells are previously heat shocked. In summary, heat treatment (1 h, 43 degrees C) inducing heat-shock proteins reduces nucleotide excision repair of UV-B-mediated DNA lesions in fibroblasts and keratinocytes during the following 24 h. This is not necessarily caused by elevated heat-shock protein levels themselves. Possibly the direct thermal damage of repair enzymes is more severe than the potential protective effects of heat-shock proteins. 相似文献
566.
Tendai J. Mafireyi Madeleine Laws John W. Bassett Pamela B. Cassidy Dr. Jorge O. Escobedo Prof. Dr. Robert M. Strongin 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(35):15259-15263
We report the first diselenide-based probe for the selective detection of thioredoxin reductase (TrxR), an enzyme commonly overexpressed in melanomas. The probe design involves conjugation of a seminaphthorhodafluor dye with a diselenide moiety. TrxR reduces the diselenide bond, triggering a fluorescence turn-on response of the probe. Kinetic studies reveal favorable binding of the probe with TrxR with a Michaelis–Menten constant (Km) of 15.89 μm . Computational docking simulations predict a greater binding affinity to the TrxR active site in comparison to its disulfide analogue. In vitro imaging studies further confirmed the diselenide probe exhibited improved signaling of TrxR activity compared to the disulfide analogue. 相似文献
567.
568.
Nanoblock coupling effect in iodine intercalated [Bi(0.82)CaO(2)](2)[CoO(2)](1.69) layered cobaltite
Guilmeau E Pollet M Grebille D Hervieu M Muguerra H Cloots R Mikami M Funahashi R 《Inorganic chemistry》2007,46(6):2124-2131
We report on the structural, microstructural, and electronic properties of iodine intercalated [Bi0.82CaO2]2[CoO2]1.69 misfit cobaltite. We first prove through a detailed and careful structural study that the block layer structure can be modified in the desired way. Iodine enters the material between the [BiO] double layers, and the c-cell parameter of the pristine compound is elongated by 3.6 Angstrom. On the basis of this result, we point out the coupling between the block-layer structure and the transport properties. Additionally, we provide in-depth commentary and discussion of some extra results, clarifying some doping effects in the quasi-2D studied phase. Finally, we also propose some expressions that might be useful to material scientists for the tuning of the properties of such compounds. 相似文献
569.
A complete E-selective synthesis of alpha,beta-unsaturated amides through a sequential reaction of a range of dichloroamides with a variety of aldehydes promoted by Rieke manganese (Mn*) is reported. A mechanism based on a sequential aldol-type reaction and a completely stereoselective beta-elimination is proposed to explain these results. The unsaturated amides obtained are readily and efficiently transformed into alpha,beta-unsaturated ketones, aldehydes, or carboxylic acids without loss of the diastereoisomeric purity of the C-C double bond. 相似文献
570.
A rapid microanalytical protein-based approach to bacterial characterization is presented. Chip gel electrophoresis (CGE) coupled with LIF detection was used to analyze lysates from different bacterial cell lines to obtain signature profiles of the soluble protein composition. The study includes Escherichia coli, Bacillus subtilis, and Bacillus anthracis (Delta Sterne strain) vegetative cells as well as endospores formed from the latter two species as model organisms to demonstrate the method. A unified protein preparation protocol was developed for both cell types to streamline the benchtop process and aid future automation. Cells and spores were lysed and proteins solubilized using a combination of thermal and chemical lysis methods. Reducing agents, necessary to solubilize spore proteins, were eliminated using a small-scale rapid size-exclusion chromatography step to eliminate interference with down-stream protein labeling. This approach was found to be compatible with nonspore cells (i.e., vegetative cells) as well, not adversely impacting the protein signatures. Data are presented demonstrating distinct CGE protein signatures for our model organisms, suggesting the potential for discrimination of organisms on the basis of empirical protein patterns. The goal of this work is to develop a fast and field-portable method for characterizing bacteria via their proteomes. 相似文献